The invention relates to a shock-absorber of the piston-and-cylinder kind for use in the landing gear of aircraft.
The invention has particular but not exclusive application to light aeroplanes or helicopters, and is most suitable for equipping landing gear of the "pendulum" type. The shock-absorber can be arranged in a substantially vertical position in which case it functions by being compressed under the load, or can be arranged in a substantially horizontal position in which case it functions by being relaxed under the load.
Shock-absorbers have been previously proposed which have the dual function of firstly serving as a shock-absorber when the aircraft is landing and/or taxiing and supporting the static weight of the aircraft when the aircraft is stationary on the ground, and secondly the function of raising and/or lowering the landing gear when the aircraft is in flight.
The invention has among its objects to provide a shock-absorber of the piston-and-cylinder kind which, in addition to the two above-mentioned functions, is also able to carry out the functions known as "dropping" the aircraft and returning the aircraft to the normal position from the dropped position, with its landing gear down, by means of a hydraulic actuating system. Dropping is the operation of lowering the aircraft, while it is supported on its wheels, beyond its normal position so as to facilitate certain manoeuvres or to improve certain characteristics of the aircraft. For example, dropping enables a helicopter to be more readily loaded into and moved within the cargo compartment of an air-freighter. It also enables the stability of a helicopter to be increased when it is resting on the deck of an aircraft-carrier or other vessel, and even on a platform floating on the surface of the sea. Finally, for the purpose of placing a helicopter on the ground in a configuration that reduces the dangerous effects of resonance waves striking the ground, it has been found very advantageous to equip the helicopter with a landing gear which enables dropping to be effected.